FIG. 1 illustrates a prior art rotary piston engine 7 which has been suggested for use as a prime mover, fluid pump or motor, and the like. Engine 7 includes a cylindrical rotor 10 mounted within a housing or stator 11. The rotor is formed along a diameter with a circular bore to provide a double-acting cylinder 12. A double-faced piston 13 is mounted for movement axially of cylinder 12 and is journalled on a crank 14 of crankshaft 15, which in turn is connected with a driving or driven shaft, not shown. The crankshaft is carried on bearings in stator 11 so that its axis of rotation 8 is parallel with the axis 9 of the rotor, with the distance between the two axes being equal to the throw radius r of the crank.
Rotor 10 will turn with an even angular velocity when crankshaft 15 is turned with an even angular velocity double that of the rotor. Piston 13 will move from one end of the cylinder to the other end as the crankshaft completes one revolution and the rotor completes one-half revolution. Total travel for piston 13 during this cycle is equal to 4r.
The above-described type of engine provides advantages in that all of the principal engine elements move with purely rotational movement. This simplifies balancing of the moving parts to avoid objectionable vibrations. Also, no connecting rods are required between the piston and crank.
One disadvantage of the described prior art engine is that a relatively large opening is required in the rotor and cylinder wall to accommodate shaft 14 throughout all of its angular positions. This requires a relatively large overall size and diameter for the engine.
Inlet and outlet ports can be provided at each side of the stator. When the rotor revolves in a clock-wise direction the piston face will recede from the stator bore surface when the cylinder opening sweeps the right half-circle of the stator, and the piston face will approach the bore surface when sweeping the left half-circle. The intake port will thus be at the right side and the outlet port at the left side of the stator bore. While such ports may facilitate the inlets and outlet connections of simple fluid pumps and motors, the valving problem becomes more acute with the application of such engines as four-stroke cycle combustion engines.